(CN) --- Fins on a fish are used for a variety of purposes, from helping them swim to serving as defensive tools. In a study released Monday, a team of researchers set out to discover how those fins developed.
The research team at the University of Konstanz in Germany wanted to examine two types of fin elements: soft fin rays, which are used for motion and are “blunt and flexible”, and fin spines, sharp and hardened fins that offer protection to fish.
In the study published in the journal PNAS, scientists demonstrated how fin spines develop in fish embryos and how such fin spines “could evolve out of ancestral soft-rays independently in different lineages of fish.” To conduct their research, the biologists studied the cichlid Astatotilapia burtoni, a spiny-rayed fish that has both soft-rayed and spiny fin parts.
The researchers began by discovering the genetic profiles of soft-ray and spiny fins as they developed in the embryo.
"What became clear from these first experiments was that a set of genes that we already knew from fin and limb development becomes differently activated in spines and soft-rays," said first author Rebekka Höch.
“In the fish fins, these genes appear to provide a genetic code that determines whether the emerging fin elements will develop looking like a spine or like a soft-ray,” the researchers said in a statement.
The research team then made note of the genetic pathways that “switch on these master regulator genes.”
"Importantly, we were able to address the roles of these pathways using chemical tools, so-called inhibitors and activators, as well as the 'gene scissors' CRISPR/Cas9 and thereby test how spiny and soft-rayed fin domains are established during development," said senior author Joost Woltering.
Using this information, the scientists were able to change the amount of the fish’s spines and soft-rays.
"We did not only see changes in the activation of the master regulatory genes, but we also observed so-called homeotic transformations, in which soft-rays had become spines, or the other way around, spines had turned into soft-rays," Woltering said.
The researchers said they want to examine fin patterning in catfish next due to the species’ ability to independently evolve spines in its fins.
"In the end we want to gain a better understanding of how new anatomical structures arise that make some species more successful than others, and how this contributed to the incredible evolutionary diversity of the fish lineages," Woltering said.
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